A casting assembly consists of a pouring cup, a gating system (including downsprues, choke, and runner), risers, sleeves, molds, cores, and other components. To produce a metal casting, metal is poured into the pouring cup of the casting assembly and passes through the gating system to the mold and/or core assembly where it cools and solidifies. The metal part is then removed by separating it from the core and/or mold assembly.
Risers or feeders are reservoirs which contain excess molten metal which is needed to compensate for contractions or voids of metal which occur during the casting process. Metal from the riser fills such voids in the casting when metal from the casting contracts. Thus the metal from the riser remains in a liquid state for a longer period of time, thereby providing metal to the casting as it cools and solidifies.
Riser sleeves are used to surround or encapsulate the riser of the casting assembly in order to keep the molten metal in the riser hot and maintain it in the liquid state. In order to serve their function, riser sleeves must have exothermic and/or insulating properties. Predominately exothermic sleeves operate by liberating heat which satisfies some or all of the specific heat requirements of the riser and limits the temperature loss of the molten metal in the riser, thereby keeping the metal hotter and liquid longer. Insulating sleeves, on the other hand, maintain the temperature of the molten metal in the riser by insulating it from the surrounding mold assembly.
Typical materials used to make sleeves are aluminum, oxidizing agents, fibers, fillers and refractory materials, particularly alumina, aluminosilicate, and aluminosilicate in the form of hollow aluminosilicate spheres. The type and amount of materials in the sleeve mix depends upon the properties of the sleeves which are to be made.
Three basic processes are used for the production of sleeves, "ramming", "vacuuming", and "blowing or shooting". Ramming and blowing are basically methods of compacting a sleeve composition and binder into a sleeve shape. Ramming consists of packing a sleeve mix (sleeve composition and binder) into a sleeve pattern made of wood, plastic, and/or metal. Vacuuming consists of applying a vacuum to an aqueous slurry of a refractory and/or fibers and suctioning off excess water to form a sleeve. Blowing consists of forcing the sand mix into the tooling with air under pressure.
More recently, it is known to prepare riser sleeves by the cold-box and no-bake fabrication process. In these processes, the sleeves are made by mixing a sleeve mix with a chemically reactive binder. The sleeve mix is shaped and cured with a curing catalyst which is reactive with the binder.
Sleeve compositions can be modified by the partial or complete replacement of the fibers with hollow aluminosilicate microspheres. See PCT publication WO 94/23865. This makes it possible to vary the insulating properties of the sleeves and reduces or eliminates the use of fibers which can create health and safety problems to workers making the sleeves and using the sleeves in the casting process.
Typically standard riser sleeves are mass produced by the supplier to fit the dimensions of the riser to be surrounded. However, in some special cases, sleeves with dimensions not readily available cannot be custom made and purchased for reasonable prices. In these cases, the user must somehow adapt a standard sleeve to meet his needs. This involves measuring the sleeve, marking the sleeve, and cutting the sleeve to the proper size. These operations result in extra time and waste.